1. Field of the Invention
The present invention relates to a recording medium delivery device for delivering a recording medium in a sheet form, which is to be mounted on an image forming apparatus such as a copying machine, a printer, and a facsimile machine, and relates to an image forming apparatus including the recording medium delivery device. In particular, the present invention relates to an improvement in stacking property of a recording medium onto a recording medium delivery tray for holding the delivered recording medium and improvement in detecting property of a fully-loaded state of the stacked recording media.
2. Description of Related Art
In the conventional image forming apparatuses, in order to ensure a stacking amount of delivered sheets and a good stacking property, a sheet delivery tray has a tray surface with its length and gradient set to a predetermined dimension and a predetermined angle, respectively, in conformity to a sheet size, a sheet delivery speed, and the like. Further, in order to prevent the stacked sheets from blocking a sheet delivery port, there is provided a full-load detecting mechanism for detecting whether or not sheets delivered to the sheet delivery tray are equal to or larger than a predetermined amount.
By the way, in some cases, the sheet having received heat and pressure by a fixing portion of the image forming apparatus may suffer from large curls (curling tendency) depending on conditions such as a paper thickness and a moisture amount of the sheet, and a roller pressure of a pressure roller of the fixing portion. When the sheet locally curls as described above, an alignment property and the stacking property of the sheets delivered onto the sheet delivery tray are remarkably degraded. Further, when a trailing end of the sheet delivered onto the sheet delivery tray is upwardly curled, the trailing end of the sheet adversely blocks the sheet delivery port before the stacking amount of the sheets reaches the predetermined amount.
In this context, conventionally, there is provided a sheet presser member, which is extended substantially perpendicularly and downwardly with respect to a sheet delivery direction from an upper portion of the sheet delivery port, to thereby improve the alignment property and the stacking property of the sheet by pressing the curled sheets. For example, there is known a configuration in which a mounting position of a Mylar (polyethylene terephthalate film) as presser means is adjusted to be in a suitable range, to thereby effectively press both right and left end portions of the sheet, which tend to easily curl in particular.
Further, there is known a configuration in which the sheet presser member is provided concentrically with the full-load detecting member, and the sheet having a small width is pressed only by the full-load detecting member while the sheet having a large width is pressed by both of the sheet presser member and the full-load detecting member, to thereby press the sheet at an appropriate pressing force in accordance with the sheet width.
However, the presser means (Mylar) and the sheet presser member described above are sheet-form or plate-form members for pressing the curls at both end portions in the width direction of the sheet, and hence it has been impossible to effectively press a curl portion in a case where the trailing end of the sheet is upwardly curled.